Web folding and cutting machines have long been known in the material handling art. Generally, such machines have the capability of performing multiple operations on either a continuous web of material or on multiple separate pieces of web fed into such machines. For example, a typical web folding machine may comprise a rotary cutting and folding device having multiple drums or rolls for performing specific functions, the rolls including feed rolls, folding rolls, knife rolls, ironing rolls and packer rolls.
With such machines, a continuous web is stored on a web supply, such as a feed stock roll, located at a first end of the device. The continuous sheet of web is either pulled or fed through a preliminary forming step which may include folding the sheet lengthwise with a folding board. The folded web can then be fed through successive rolls within the machine that perform various sequential operations on the material, to include pulling the continuous web off of the feed stock roll, cutting the continuous web into segments having a predetermined length, folding the segments a predetermined number of times into folded articles having a predetermined folded length, and packing the folded articles in preparation for later packaging operations.
With regard to web folding operations, these rotary folding devices may utilize a set of cylindrical pull rolls, located downstream from the web supply, that use frictional forces existing between the web and roll outer surfaces to pull the web from the feed stock roll and feed it to a pair of folding cylinders. The folding cylinders co-act with one another to tuck and grip the web to create one or more folds in the web received from the pull rolls. With the tuck and grip method, as the web is deposited between a pair of folding cylinders, a pointed tucker blade located on the surface of one of the cylinders pushes or tucks the material into a space existing between the jaws of an open gripper located on the surface of the opposite cylinder, thus creating folded web segments having a predetermined length. This predetermined length is a function of the circumference of the outer surface of the folding cylinders existing between the tuck and grip mechanism located thereon.
As the shortest folded segment that a given folding machine is capable of producing is a function of the circumference of the folding cylinder's outer surface existing between the tuck and grip mechanisms located thereon, operators of present machines wishing to create a folded segment having a length shorter than the cylinder's circumference must replace the folding cylinders themselves with cylinders having a smaller diameter. Such cylinder replacement requires disassembly of the machine, resulting in costly production down-time. Thus, present cutting devices suffer the disadvantage of requiring a disassembly of the machine to decrease the length of folded web segment shorter than that which is possible of folding cylinders of a given diameter.
Rotary folding machines also suffer disadvantages resulting from the inherent complexity of the devices themselves, with problems such as material tearing or jamming occurring in the feeding, cutting, folding and packing operations performed on the web. For example, many prior art folding machines have rolls located upstream from the folding cylinders such that the upstream rolls and folding cylinders are displaced from one another by a given distance, thus creating an open space or gap between one or more of the upstream rolls and one or more of the folding cylinders. In transferring the web from the upstream rolls to the folding cylinders, it must traverse the open space or gap located there-between, thus increasing a likelihood of a jamming of the web material during a transfer of the web to the folding cylinders. Thus present web folding machines suffer the disadvantage of web jamming during a transfer of the web to the folding cylinders from upstream cylinders.
Present machines also suffer from disadvantages present during the folding operations themselves. In utilizing the tuck and grip method to create folds in the web, from the time the web is released from a given gripper until the time that it is gripped again on the opposite folding cylinder, the length of web is held in place on the surface of the cylinder only by the friction existing between the respective cylinder's surface and the web material. However, this friction may be insufficient to effectively hold the web, thus allowing slippage to occur between the web and folding cylinder outer surface. Thus, present machines suffer the disadvantage of slip occurring between the web and cylinder, causing the web to be gripped in the wrong location or resulting in a jamming of the machine due to an improper positioning of the web on the cylinder.
Also, present folding devices utilizing the tuck and grip method commonly use a tucker blade that is mounted to the cylinder via a pivoting bearing. The pivoting bearing enables the tucker blade to rotate slightly as it retracts from the space between the gripper jaws during the grip cycle, with the blade later returning to its original, un-rotated position via the force of a return spring. However, as is common in web processing operations, a build-up of dust or other debris may occur within the working parts of the rotating tucker blade that prevents the tucker blade from returning to its original, un-rotated position. If the tucker blade cannot return to its original, un-rotated position, it will cause damaging interference between the gripper jaws and tucker blade during the next revolution of the folding cylinders. Thus, because present folding devices have a tucker blade that is prone to interference from dust and debris, they suffer the disadvantage of jamming and causing damage to the folding cylinders themselves.
Furthermore, mechanical folding cylinders using the tuck and grip method presently place the gripper face on the radius defined by the outside diameter of the folding cylinder. The tucker blade thus protrudes from the opposing folding cylinder outside diameter by the distance required to sufficiently push the material into the gripper jaws. However, this configuration results in a tucker blade that protrudes significantly from the surface of the cylinder, thus resulting in both the web following a non-symmetrical path as it wraps around the folding cylinder and an increased likelihood of tearing. Because many folding cylinders have this protruding tucker blade configuration, they suffer the disadvantage of being prone to tearing the web material as it wraps around the folding cylinder and tucker blade.
The gripper jaws of present folding cylinders are cam-driven to an opened position and spring-biased or cam driven to a closed position. A cam follower attached to the moving gripper jaw follows a fixed cam typically mounted to a frame of the device. During a timing adjustment of the gripper jaws (an adjustment of the time period during which the jaw remains open or closed), the cams mounted to the frame must be moved to accommodate a desired change of time. However, because the cams of many present machines are bolted to the frame, the operation of the machine must stop to allow the operator to manually adjust the cam position through a loosening and tightening of the bolts that hold the cams to the machine frame. Because present machines require that its operation be stopped to make a cam (timing) adjustment of the gripper jaws, they suffer the disadvantage of inefficiency due to the costly “down time” required of the adjustment during article production.
During the production of folded articles, it may be useful during production to periodically elevate the web fed into the folding machine to produce a folded product having a location vertically displaced from surrounding folded articles. Such a displaced article may serve as a visual numerical marker for indication of the number of folded articles produced during production. Present folding machines periodically adjust the angle of the folding board to raise the elevation of the web fed into the machine. However, such an adjustment may result in a tearing of the web itself flowing over the folding board. Thus, present machines suffer the disadvantage of tearing the continuous web by periodically adjusting the angle of the folding board to create a displaced marker within the folded product.
Many present folding devices utilize a packing system that moves the folded articles from the surface of the folding cylinder to a conveying system that both segregates predetermined quantities of folded articles and moves the quantities away from the folding cylinders towards a packaging operation (not discussed). These packing systems often utilize packing fingers that pivot away from the cylinder to lift and move the folded article from the surface of the folding cylinder to a screw conveyor. The screw conveyor, which comprises one or more helical screws positioned generally perpendicular to the folding cylinders, accepts a predetermined quantity of folded articles from the packing fingers to between the flights of the screw to establish the segregated quantities of folded articles.
After a pre-determined quantity of folded articles is moved to between the screw flights, the screws rotate to move the quantity laterally away from the folding cylinders and towards the packaging operation. However, the quantity of folded articles placed between the flights of a given screw is limited by the pitch of the screws themselves and the thickness of the folded articles packed therein. Thus the quantity of the folded articles placed therein cannot have a combined width that exceeds the flight-to-flight distance. To accommodate such a quantity, an operator has to change the helical screws of the machine to have a pitch wide enough to accept a given quantity of fold articles made from a web material of given thickness, again resulting in costly production down time. Present machines using such screw packing systems thus suffer the disadvantage of requiring the operator to change helical screws to accommodate a variety of web material thicknesses and folded articles quantities.
Thus, there is a need for an apparatus and method that overcomes the disadvantages of: requiring a disassembly of the machine to vary the folded length of the finished product; web jamming during web transfer to the folding cylinders; creating improperly folded articles or incurring machine malfunction due to web slippage against the folding cylinders; incurring machine malfunction due to the tucker blades not returning to a non-rotated position; tearing the web material due to the substantial protrusion of the tucker blade in relation to the cylinder surface; incurring machine down-time due to manual timing adjustments of the gripper jaw cams; tearing the continuous web by periodically raising the folding board to create a visual marker; and inefficiency of operation due to a changing the conveying screws to accommodate a variety of product quantities and thicknesses.